Bulk diffraction grating (BDG) based multiplexer/demultiplexer (Mux/Demux) devices have recently found application in dense wavelength division multiplexing (DWDM) optical communication systems. Compared to other techniques for processing DWDM optical signals (e.g., fiber Bragg grating, arrayed waveguide grating, thin film filters), BDG provides an economical way for high channel count DWDM solutions. However, a drawback that limits the application of BDG devices is its Gaussian-shape spectral response. As a result, any drift or offset of a frequency from its specified value (e.g., an ITU frequency) may result in significant loss of that frequency. Although the laser source can be controlled and the frequency stabilized to prevent frequency hopping, there is typically some frequency drift that will occur. In addition, a BDG device also could have its actual channel centers deviate from their designed frequency due to mechanical movement or temperature fluctuation.